<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
<title></title>
</head>
<body>
<script type="text/javascript">
function output(y,m,d){
	alert(y+"年"+m+"月有"+d+"天");
}
function days(y,m){
	if(m == 2){
		if((y%4 == 0 && y%100 != 0) || (y%400 == 0)){
			output(y,m,29);
		}else{
			output(y,m,28);
		}
	}else if(m == 4 || m == 6 || m == 9 || m == 11){
		output(y,m,30);
	}else{
		output(y,m,31);
	}
}
days(2021,6);
</script>
</body>
</html>
